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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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 Posted: Tue Jan 13, 2009 3:51 am Post subject: Jan 13 VH |
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After a week's wait for a VH, an xy-wing (679) does it.
Earl |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Tue Jan 13, 2009 12:22 pm Post subject: |
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Same for me. Kinda disappointing.  |
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Wendy W
Joined: 04 Feb 2008
Posts: 144
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| Posted: Tue Jan 13, 2009 11:03 pm Post subject: |
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| It's even worse for me. The past 2 VH puzzles I've done with no advanced techniques whatsoever. One I'd put down to luck -- or a mistake. But two in a row?! |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Tue Jan 13, 2009 11:41 pm Post subject: |
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| Maybe you won't find my Set H Puzzle 85 so trivial. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Wed Jan 14, 2009 1:38 am Post subject: |
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| Wendy W wrote: | | It's even worse for me. The past 2 VH puzzles I've done with no advanced techniques whatsoever. One I'd put down to luck -- or a mistake. But two in a row?! |
Wendy, when that happens, do you ever try it a second time? I have and have been unable to duplicate my first solution at times. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Wed Jan 14, 2009 5:22 pm Post subject: |
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After basics: | Code: | +----------------+----------------+----------------+
| 2 5 39 | 4679 367 3467 | 8 37 1 |
| 79a 67-9 367-9 | 1 8 2 | 39b 4 5 |
| 4 1 8 | 79 5 37 |2-39 237 6 |
+----------------+----------------+----------------+
| 59 69 2 | 3 1 8 | 7 56 4 |
| 3 8 67 | 45 67 45 | 1 9 2 |
| 57d 4 1 | 267 267 9 | 35c 3-56 8 |
+----------------+----------------+----------------+
| 8 23 5 | 26 9 36 | 4 1 7 |
| 6 79 79 | 8 4 1 | 25 25 3 |
| 1 23 4 | 257 237 357 | 6 8 9 |
+----------------+----------------+----------------+ |
Take a look at a-b-c-d-a. The solutions are:
or
and you can make the eliminations shown.
Keith |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Wed Jan 14, 2009 6:07 pm Post subject: |
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| Keith, is that considered a standard XY-Chain or is there something else about it? |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Wed Jan 14, 2009 8:32 pm Post subject: |
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| Marty R. wrote: | | Keith, is that considered a standard XY-Chain or is there something else about it? |
Marty,
Sudoku Susser calls it a loop. (Edit: I also just saw a mention of a "bidirectional cycle" which is probably the same thing. Or, maybe it is a bicycle with a reverse gear.)
It is bidirectional. For example, choose <7> in a, the implications traverse the loop counter-clockwise. Choose <9>, the implications are clockwise.
You can see how I found it. I was looking for an extended XY-wing. We have 79 - 39 - 35 - 57. Regard any two adjacent cells as a pseudocell, for example 79 - (59) - 57 and you have an XY-wing.
The point is that the pincer cells a and d can see each other. You may recall that re'born pointed this out in an M-wing a couple of weeks ago.
http://dailysudoku.co.uk/sudoku/forums/viewtopic.php?t=2143
If the pincer cells are peers (buddies) then you have a loop, and each pair of adjacent cells in the chain potentially makes eliminations.
I don't know if these are rare or not. They are not often mentioned, which may be because most solvers (human and otherwise) do not look for them.
Keith
Last edited by keith on Wed Jan 14, 2009 10:24 pm; edited 1 time in total |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Wed Jan 14, 2009 9:14 pm Post subject: |
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Keith,
I wouldn't say they are rare.
Myth Jellies calls them a Bi-location Loop in his players forum post on AIC's. this is a special case of a AIC loop because each cell contains only two candidates. the two candidates within the cell are connected strongly, and the cells are connected weakly.
since the loop connects the bi-value cells weakly, you can cut the loop at any of those weak links and still have a true xy-chain.
this will make the eliminations you pointed out.
yours is a square and therefore more easily recognized, some can get very elaborate especially if they involve more than 5 cells and two or more cells occur in the same box 
| Code: | not2 not5
not2 not5
not2 not5
not4, not4, not4 (4=2)---not4----(5=4) not4, not4, not4
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not2 not5
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not8, not8, not8 (2=8)---not8----(8=5) not8, not8, not8
not2 not5
not2 not5
not2 not5 |
(4=2)-(2=8}-(8=5)-(5=4)
edit: corrected for errors
Last edited by storm_norm on Wed Jan 14, 2009 10:25 pm; edited 1 time in total |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Wed Jan 14, 2009 10:05 pm Post subject: |
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Norm,
| Quote: | | some can get very elaborate especially if they involve more than 5 cells |
You mean, like this:
| Code: | +----------------+----------------+----------------+
| 2 5 39 | 4679 367 3467 | 8 37 1 |
| 79a 679 3679 | 1 8 2 | 39b 4 5 |
| 4 1 8 | 79 5 37 | 239 237 6 |
+----------------+----------------+----------------+
| 59h 69g 2 | 3 1 8 | 7 56f 4 |
| 3 8 67 | 45 67 45 | 1 9 2 |
| 57i 4 1 | 267 267 9 | 35c 356 8 |
+----------------+----------------+----------------+
| 8 23 5 | 26 9 36 | 4 1 7 |
| 6 79 79 | 8 4 1 | 25d 25e 3 |
| 1 23 4 | 257 237 357 | 6 8 9 |
+----------------+----------------+----------------+ |
Keith
Last edited by keith on Wed Jan 14, 2009 10:31 pm; edited 1 time in total |
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sudocraz
Joined: 28 Apr 2008
Posts: 53
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| Posted: Thu Jan 15, 2009 2:13 am Post subject: |
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At least my husband and I are getting a lot of practice with xy-wings. We are pretty good with them now. They even might be beginning to be a little boring. 
Are the xyz wings pretty much the same as xy-wings, except one square , I assume the pivot square, has 3 numbers? |
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DennyOR
Joined: 12 Sep 2007
Posts: 33
Location: Portland, Oregon
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| Posted: Thu Jan 15, 2009 9:44 pm Post subject: |
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| A 79s w-wing in columns 1 and 2 did it for me. |
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